Microsoft currently has the Windows Genuine Advantage (WGA) checking each day to make sure you are running a legal version of Windows. If you are not running a legal copy then it will display the notification pictured above each time you start your computer. This whole thing frustrated many people so Microsoft put together a guide for removing the software/spyware that displays the notifications.
M-Dollar was discussing a conversation with a Microsoft representative where the rep said
In the fall, having the latest WGA will become mandatory and if it’s not installed, Windows will give a 30 day warning and when the 30 days is up and WGA isn’t installed, Windows will stop working, so you might as well install WGA now.
Some say that Microsoft will implement this system as soon as September. That means that we may no longer have to fear a notification, instead we will have to fear being locked out of our computer!